CSS code inspection - ignore particular syntax issue

GTK+ 3 has it's own barstardised version of CSS: GTK+ CSS Overview

The custom CSS nodes are not a problem - Rider allows you to "Add as custom HTML" tag.

What I can't seem to get Inspector Code to accept/ignore is the GTK CSS @define-color rule that allows me to get the user-specified colors from the current OS theme like this:

background-color: @theme_bg_color;

The Code Inspector just highlights it as "a term expected"...

It doesn't have the usual options in the popup menu to allow me to look at the inspection rule.

Am I able to edit the CSS code inspection rules somehow, so it will accept this non-standard syntax?

Or can I do the equivalent of this somehow?

// ReSharper disable once InconsistentNaming

Thanks.